It is known that the piloting devices (control columns, rudder bars) of modern aircraft are easy to handle by the pilot and/or the copilot of said aircraft, the tilting of the latter possibly being very fast. On the other hand, the actuators of the movable aerodynamic surfaces of the aircraft (ailerons, flaps, control surfaces, etc.), controlled from these piloting devices, cannot respond instantaneously to the piloting orders generated by the latter. There may therefore be, at high piloting amplitudes, a significant phase shifting between the displacement of a piloting device and that of the movable aerodynamic surfaces that it controls.
The result of this is that the pilot, observing that the response of the aircraft is delayed, may have a tendency to further increase the tilt amplitude of said control member. By then, when the delay time has elapsed, the response of the aircraft becomes far greater than planned, so that the pilot rapidly reverses the tilt of said control member, so that the same situation is repeated in a movement in the opposite direction, and so on. There therefore appears, in the aircraft, induced pilot oscillations—generally referred to PIO in the aeronautical field, which can deteriorate piloting accuracy.
To try to resolve such a problem, it is known to increase the dimensioning of the actuators of the controlled aerodynamic surfaces and their hydraulic and electrical power supplies, which increases the costs and weight of the aircraft. Such cost and weight increases can become critical for large aircraft.
Also known are piloting systems equipped with non-linear filters for processing the piloting order and converting it into a piloting order free of oscillations corresponding to induced pilot oscillations.
However, such non-linear filters present the drawback of attenuating certain piloting orders (for example, abrupt high-amplitude orders) which do not however correspond to induced pilot oscillations and consequently should not be attenuated.
Furthermore, the non-linear filters of these piloting systems do not allow accurate control of the speed of amplitude variation of the control orders intended for the actuators of the movable aerodynamic surfaces.